It has been desired to additionally print a mark such as an underline and the like adjacent to particular characters printed on the paper by the printer so that the end of a paragraph or the position of the particular characters is conveniently identified
Heretofore, different color printing has been generally used to identify the particular characters so as to discriminate debits from credits in accounting, or the input from the output, or the process in accounting from the result. To this end, it is necessary to use two ink ribbons having different colors from each other or to provide two sets of printing rings when ink rollers having different colors are used for each of sets of printing rings.
When ink ribbons are used, the quality of printing tends to be poorer in comparison with printing using ink rollers, and the ribbons tend to be twisted or deflected during the operation thereby causing failure in printing or unevenness of printing. when the ink rollers are used, the construction of the printer is made very complicated thereby raising the manufacturing cost.